1. Field
The following description relates to a varifocal lens for a camera module incorporated in a wireless mobile communication device.
2. Description of the Related Art
A wireless mobile communication device, such as a mobile phone, has evolved to provide a variety of functionalities, such as camera, game, music, broadcast, and Internet, as well as voice and message communications.
In addition, it has been attempted to fabricate a more compact electronic device equipped with more functionalities. A camera module is one of devices which are very difficult to reduce in size.
A phone camera is generally designed to take pictures at a minimum distance of 60 cm, and thus a picture of a business card taken at a distance of about 5 to 10 cm is blurred. To address this problem, several auto-focus technologies using a voice coil motor (VCM) or a step motor have been proposed. However, most of these technologies are disadvantageous in thickness, volume, noise, etc.
Accordingly, a varifocal lens has been proposed which uses a fluid lens part to change a focal length. The varifocal lens is configured to change a curvature of a fluid lens part as optical fluid is injected into or discharged from the fluid lens part.
However, the edge of the fluid lens part is fixed in the varifocal lens, which causes a limitation in profile when the curvature is changed. More specifically, when the fluid lens part is changed to be convex or concave, the fluid lens part only has a specific conic profile since the edge of the fluid lens part is fixed, which may cause a degraded optical performance and a problem in optical design of the entire module. This may also cause a restriction to optical applications.
For example, in a case of an optical design requiring a fluid lens part of a spherical profile, only a small central portion of a fluid lens part of a specific conic profile can be used since only the small central portion is spherical. Accordingly, the entire fluid lens part needs to be spherical to use a wider portion of the lens part.
On the contrary, the fluid lens part needs to be changed in profile for optical designs requiring a sharper conic profile and an aspheric profile.